Tow target and signal producing accessory



March 8, 1960 DEL MAR 2,927,793

TOW TARGET AND SIGNAL PRODUCING ACCESSORY Filed Feb. 14, 1958 2 Sheets-Sheet l March 8, 1960 B. E. DEL MAR 2,927,793

TOW TARGET AND SIGNAL PRODUCING ACCESSORY Filed Feb. 14, 1958 2 Sheets-Sheet 2 Tow TARGET AND SIGNAL PRODUCING ACCESSORY Bruce E.- Del Mar, Pacific Palisades, Califi, assignor to Del Mar Engineering Laboratories, Los Angeles, Calif.,

a corporation of California 7 Application February 14, 1958', Serial No. 715,467 I 16 Claims. (Cl. 273-1053) This invention relates to an apparatus for use on an airborne vehicle to produce visible signals, for example smoke signals, for assistance in visual identification and tracking. More particularly described, the invention is directed to such an apparatus in cooperating combination with an aerial tow target. 7

In the use of tow targets for giving military personnel realistic experience in detecting, tracking, intercepting and destroying airborne vehicles, there are occasions when it is highly desirable to create visible signals such as smoke signals at the tow target. Inmany instances, for example, personnel observing and evaluating aerial target practice either from the ground or from an aircrafttfind it diflioult to locate the tow target and orient its direction of travel in space, since a tow target is relatively small and may be many thousands of feet from the towing airplane' There are other instances Where quick identification of thetow target and its direction of travel by smoke signals is a precaution that eliminates the possibility of inadvertently attacking something other than the tow target. g

One of the problems to which the invention is directed is to equip a tow target for generating a visible self-sustaining signal in space by remote actuation. The remote actuation may be by electrical communication from the towing aircraft along the'tow line or may be by radio from a control station anywhere.

' 7 Another problem is to equip a tow target to produce a plurality of visible self-sustained signals in controlled sequence. The individual visible signals may be used at widely different times in the course of a target run or, if desired, may follow each other with only brief intervening time periods.

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' A further problem is to produce a highly visible smoke signal with relatively light and compact equipment. .The greater the bulk and weight of the smoke generating apparatus together with the control system, the less the quantity of signal-generating material that can be carried a by the tow target.

A still further problem is to provide a simple and inexpensive mechanism for releasing the signal-generating 'materials. This objective is especially important in the use of a tow target which may not survive for reuse.

In general, the preferred practice of the invention meets inaterial from the containers, and by employing ram air and centrifugal force to empty the containers and to discharge the material into the atmosphere. The invention avoids the necessity of carrying any compressed gaseous body for discharging the material and further avoids the *necessity of any discharge mechanism with relatively movable parts. V f A feature of the invention is the manner in which it utilizes two cooperative forces for discharging thesignalcreating material both of which forcesare derived from V 7 2,927,793 Patented Mar. 8, 1960 the flight of the tow target itself. One of these forces is an air stream that is directed through each container to sweep the signal-generating material into the, atmosphere. For this purpose, a high pressure differential is created by using ram air for high pressure at the inlet end of an air passage and by further using the slip stream adjacent the tow target to create a suctionv effect at the discharge end of the air passage. The other of the two cooperating forces is centrifugal force created by positioning the discharge passage radially: of the axis of the tow target and rotating the tow target aerodynamically about its axis.

The signals for detonating the explosive squibs may be transmitted along the tow cable but in the preferred practice of the invention, radio signals are employed. For this purpose, the tow target carries'a radio receiver, an electromotive source and a stepping switch for connecting the electromotive source to the explosive squibs in sequence.

The various features and advantages of the invention will be apparent from the following detailed description together with the accompanying drawings.

In the drawings, which are to be regarded as, merely illustrative:

Fig. 1 is a side elevation of the preferred embodiment of a tow target of the invention with portions broken away; i

Fig. 2 is a side elevational view on an enlargedscale of a container of the signal-creating material, the con.- tainer being shown with an inlet air passage and an outlet air passage, both of which are normally closed by explosive squibs; I

Fig. 3 is an enlarged fragment of Fig. 2 showing the explosive squib at the end of the outlet passage;

Fig. 4 is a similar view showing the explosive squib'at the inlet passage; 7 v

Fig. 5 is a transverse section of the explosive squib of Fig. 4 together with the surrounding wall;

Fig. 6 is a view similar to Fig. 5 showing how the wall surrounding the squib is ruptured by detonation of :the squib;

Fig. 7 is a perspective view of the tail-end of the tow target showing the arrangement of the containers for the signal-creating material; and I Fig. 8 is a wiring diagram of the system for remote control of the plurality of explosive squibs.

The tow target shown in the drawings has a stream;- lined body, generally designated 10, which may comprise a suitably reinforced thin-walled shell 12 of molded paper. The body 10 is provided with a set of tailvanes 14 which have slightly angular tip portions 15'to serve as aerodynamic means for causing the body to rotate about its longitudinal axis. The tail vanes 14 may be made of foamed cellular plastic adhesively bonded to the body 10, and the body may be internally reinforced with the same material. t

The streamlined body 10 preferably has an integral rigid probe or nose member, generally designated 16, that is of slender tapered configuration and is capable of serving as the sole support of the target body prior to-a target run. Thus, the tow planefor the target run may be provided with a launching means for the tow target, as indicated at 17 in Fig. l, the launching means being of relatively small cross-sectional dimension and being adapted to telescopically receive the nose probe 16.for support of the tow target until the beginning of a target run.

In the construction shown, the nose probe 16 comprises a thin-walled axial tube 18 of aluminum orv the like, the base end of which is attached to a bulkhead member 20 of the body structure and is reinforcethby a surrounding ring 22. The axial tube 18 exteudstthrough ward relative to the direction of flight.

.a secondconical reinforcement ring 24 at the leading end of the body 10, and, if desired, the adjacent portion of the body shell may be made of glass fibers impregnated -with polyester resin for increased strength. The'nose probe-16 is.adapted for attachment to a 'tow cable 25 andiis provided witha suitable rotary joint for-this purpose. r111 tthe .constructionshown, a clevis 26 fordirect connection to the towacable is rotatably mounted in a sleeve. 28..at the leading end ofthe nose-probe 16.

,Itzispcontemplated that the tow' target' body-1t) will incorporate suitable radar corner-reflector means to facilitate detection. of the-tow. target by reflection of radar waves impinged upon it, which corner-reflector means may becapable of- .either monostaticor bistatic reflectivity or both. In this instance, the tow target-body incorporates acompositei-corner-refiector unit that is generally designatedby numeral 30.

*This reflector unit fiii may include a-transvcrse metal foil sheet 32 sandwiched into a thick transverse Wall 34 offoamed cellular plastic material. A second longitudinalmetalfoil sheet 35 is sandwiched into a thick longitudinal wall 36 of foamed cellular plastic, and'a third metal foil shcet '33 is sandwiched into a third longitudinal wall 39- of foamed cellular plastic. The three metal foil sheets are in three planes that are perpendicular to each otherand meet at a comon center. The composite corner-reflector unit 30 spans the interior of the' body shell 12".to. serve-as reinforcement therefor and is secured between two=spaced reinforcement bulkheads 40 and 41. The signal-creating apparatus includes a plurality of concentrically distributed longitudinal cylindrical housings 42which-are open at'their-trailing ends and which are: faired into theconfiguration of the tow target .body at:their forwardeuds' as shown in Fig. 1. In the .construction shown, there are four of the cylindrical housings 42'interposed-between the four tail vanes 14 at relatively short radial distances'from'thelongitudinal axis 1 of the, tow target body. Each of'the cylindrical housings 42 telescopically receives a cylindrical container 44 of signal-creating material which container is suitably secured in a positionextending rearward into the slip stream. As-bestshown in'Fig. 2, each of the containers 44 is closed by a forward wall 45 inside the corresponding cylindrical housing 42 and by a rearward exposed end walk-46. -An inletair'tube 48 is .mountedin the rear end wall 46 for communication with the interior of' the container-aridan outlet tube50 is also mounted in the same rear end wall to serve as adis'charge passage means for the signal-creating material. The container '44 may -als'o;have-.a.=filler aperture "closed by 'a plug 51. (Fig. 7). "The inlet end oftheinlet air tube 48 is closed by. an explosive squib 52 which may be cemented in place in a' fiuidtight manner. Asshown in Figs; 4 and 5, the wall oftheinlet air tube surrounding thev explosive squib 52 is relativelythin on the side in the'direction of flight,

thetube beingformed with'a thin wall portion 54that is'ea'sily ruptured'by the explosive'forceofthe squib. When the squib 52 is, detonated, the thicker wall portionsbf the-inlet airtube remain intact but this thinwalled-portin 54is ruptured outwardly. Fig. 6 shows how' the' rupturing'etfect of the explosive force of the squib-*ma'y form two "wings 54a and 54b of, the thin wall portion-54-thereby forming a ramppening 55, that faces-"forward;to-cause'the'creation therein of relatively high- .pressure --byram air.

-"-':*In like manner, the outlet tube 50 .is closed, at its outer end'by a second explosive squib' 56. .and the tube islformed witha' thin-walled portion 57'that faces rear- -It is apparent that-detonation ofthe gexplosive squib .56 will form an openi ng"that-issimilar"toitheram opening 55 but is di- -rected rearward for the creation of a relatively low pres- -suresin -the---opening by the suction effect of the slip streamsadjacent theatow target.

The explosivesquibs 52 and 56 are designed to be detonated electrically and suitable provision is made for connecting wiring to the two squibs. For this purpose, each container 44 may be provided with an axial tube 58 that extends through both of the end walls 45 and 46 .to permit wiring to be run through the length of the container. As shown in Fig. 2,-the leading end of thecontaincr 44 may be formed with a plug-in electrical fitting 59 that surrounds the forward end of the axial tube 58. The fitting 59 is of the bayonettype with a pairofbayonet lugs 63 and mates with a complementary fixed female fitting to hold the container 44 in mounted position. A

1 pair of wires 61 extend from the electrical fitting 59 through the axial tube 58 to. the two explosive squibs 52 and 56 respectively.

Any suitable signal-creating material may be used in the containers 44 to create the desired visible signals. For example, the containers may be filled with highly combustible material for ignition by detonation of the squibs to produce a flame for visibility at night or the containers may be filled with a suitable pyrophorous that will ignite upon contact with the oxygen of the atmosphere for the same purpose.

In this particular practice of the invention, however, the containers 44 are filled with materials for the creation of smoke signals for observation by daylight. The containers may be filled with titanium tetrachloride,'for example, which reacts with the moisture of the atmosphere to produce smoke. If desired, the containers'may be filled with chemicals which react to create smoke without assistance from the atmosphere. In some prac tices of the invention, the containers may be filled with inert powder andthe powder may be colored toproduce a colored smoke signal.

The explosive squibs 52 and 56 associated with the plurality of containers 44 may be ignited by means, ineluding abattery 62 under the control of a radio receiver 64. In the present arrangement, the battery 62 andthe radio receiver 64 are mounted on a housing 65 on'the front face of the reinforcement bulkhead 40. The housing 65 contains control components that are electrically connected with the explosive squibs by conductors in a cable 66, the cable extending through the radar cornerreflector unit 30. The radio receiver may, for example, operate on a fixed frequency in the range between 200 and 400 megacycles and may be responsive to a particular tone or modulation frequency for control from one or more remote control stations. The remotecontrol station may be on the ground or may comprise a transmitter on, an airplane and the airplane may. be the tow plane or may be an observation plane.

The tail ,fin structure of the tow target may be utilized toflprovide anantenna of substantially larger dimension than the cross dimension of the tow target body. .Such an antenna, which is generally designated by numeral 68 in Figs. 1 and 8, may comprise two halves of a dipole and, as indicated in Fig. 8, may be connected to the radio receiver, 64 by. means of a sheathed cable, generally designated by numeral 70. Two arms 72 of the antenna are connected to the sheath 75 of the cable'70 and the other two arms 74 are connected to the inner conductor 76 of thecable. I

' The control system for detonation of the various; pairs of explosive squibs 52 and 56 may include the .components shown in the wiring diagram in Fig. 8. :When the radio receiver 64. is in operation and receives a radio signal to which it is tuned, it closes a circuit, by relay operation for electrical detonation of. the, squibs. This circuit includes a normally closed switch 78"which is connectedto theradio receiver 64 by awire 80. The normally closed switch 78 is connected bya wire 811 to a rotary solenoidgthat is represented by a coil,.82, the second side of'the coil being grounded. The ,switCh;.-.78 is also connected by awirei 84. to a switch arm of. a rotaryswitch, the switch arm 85 being operatively conid nected to the rotary solenoid 82 for actuation thereby as indicated by the dotted line. 86. The rotary switch arm 85 is movable step-by-step from a starting position represented by a contact 88 to four consecutive contacts 90, 91, 92 and 93 in sequence.

As shown in Fig. 8 one side of each of the explosive squibs 52 and 56 associated with one of the four containers 44 is connected to the contact 90 of the stepping switch by a wire'94 and the other sides are grounded. In like manner, the explosive squibs 52 and 56 associated .vides a rearwardly directed opening in the discharge end of the outlet tube 50. It is apparent that the two tubes 1' 48 arid 50- in combination with the container 44 form an air passage for sweeping the contents of the container with a second container 44 are connected to the contact 91 by a wire 95; the explosive squibs 52 and 56 of a third container 44 are connected to the contact 92 by a wire 96; and the explosive squibs of the fourth container are connected to the contact 93 by a wire 97.

The filament circuit of the radio receiver 64 includes a battery 98 that is grounded inside the radio receiver by a Wire 100. During a target run with the tow target at the end of a tow cable, a filament-energizing circuit is closed by two normally closed switches 102 and 104 in series. These two switches are connected to the battery 98 by a wire 105 and are connected to the filaments of the radio receiver by a wire 106. i

The switch 102 is a normally closed switch positioned as indicated in Fig. 1 to be opened by contact with the launcher 17 so that the squibs may be detonated only when the tow target is out of the launcher. The switch 104 is also a normally closed safety switch that operates in unison with the previously mentioned switch 78 as indicated by the dotted line 108. The two switches 78 and 104 are open to keep the squibs from being detonated when the tow target is on the ground and away fromthe launcher. As shown in Fig. 1, the two switches 78 and 104 may he opened in unison by insertioncf a safety pin3110.. It' is contemplated that the safety pin 110 will be conspicuous and for this purpose a brightly colored ribbon may be added if desired. When the tow target is onthe ground with the safety pm 110 inserted, the filament circuit may be closed by a normally open switch 112 which is connected to the wire 105 by a wire 114 and is connected to the wire 106 by a wire 115. This alternate filament-energizing circuit is used whenever a headphone set (not shown) is plugged into the radio receiver for the purpose of tuning the receiver to a test signal. The headphone set is plugged into an audio jack, generally designated 116, and the normally open switch 112 is operatively connected to the audio jack as indicated by the dotted line 118 to close in response to the insertion of the headphone plug.

The manner in which the invention serves its purpose may be readily understood from the foregoing description. In preparation for a target flight, four containers 4,4 filled with the "signal-producing material are inserted and secured in the four cylindrical housings 42 and the explosive squibs52 and 56 of the four containers are connected to the control circuit in the manner indicated by the diagram in Fig. 8. The rotary switc'h'arm 85 is placed at its home position on the contact 88; the tow target is engaged with the launcher 17; and the safety pin 110 is withdrawn. As the practice area is approached, the tow target is launched by reeling out the tow cable 25 in preparation for an actual target run.

Whenever detonation of a pair of explosive squibs 52 and 56 is desired during a target run, a radio signal from a remote control station is sent to the receiver 64 to cause momentary energization of the wire 80. Momentary energization of the wire 80 actuates the rotary solenoid 82 to advance the switch arm 85 one step to the contact 90. The movement of the switch arm 85 to the contact 90 completes a firing circuit through the corresponding pair of explosive squibs 52 and 56 associated with the first container in the sequence.

The detonation of the squib 52 provides a forwardly directed opening for the entrance of ram air into the inlet air tube 48 and the detonation of the squib 56 promaterial into the air;

into the atmosphere. It is further apparent that with the pressure of ram air on the inlet end of this passage and with the suction effect of the slip stream on the discharge end of the passage, a high magnitude pressure differential is created across the passage to cause air to sweep through thecontainer with effective force and velocity to entrain the smoke-creating material and carry the material into the atmosphere.

Since the two air tubes 48 and 50 are aligned on a radius from the longitudinal axis of the tow target body and since the tow target body rotates about this longitudinal axis, highly efiective centrifugal force is created that favors the movement of air into the container through the inlet air tube 48 and favors to even greater degree the movement of air and the entrained material outward through the discharge tube 50. Thus, two forces cooperate for effective emptying of the container, namely, the force of the airflow and centrifugal force.

Subsequent radio signals may be sent to the radio receiver 64 to energize the wire to cause the arm of the rotary switch to advance'successively through the series of remaining contacts 91, 92 and 93 to cause the remaining three containers 44 to be discharged in controlled sequence into the atmosphere.

Whenever the tow target is on the ground the safety pin is inserted to open the normally closed safety switches 78 and 104. With the safety pin 110 inserted, the headphone set may be safely plugged into the audio 'jack 116 for tuning the-radio receiver to a test signal.

Since the safety pin 110 holds the switch 78 open, there 'is no possibility of the explosive squibs being detonated by the radio receiver during the tuning procedure.

When the target is in the launcher 17, the launcher holds the normally closed safety switch 102 open to prevent energization of the filaments and thus makes it imbodiment of the invention will suggest various changes,

substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

I claim: H 1. In combination with an airborne vehicle, means to provide visible signals for detection and flight path orientation at great distances comprising: a container for ma- "terial capable of producing a visible signal in the atmosphere; a normally closed passage means for directing ram air into and through the container to discharge said explosive means for detonation to open said passage means for discharge of said material; and remotely controlled means to detonate said explosive means.

2. A combination as set forth in claim 1 in which the discharge end of said passage means extends rearwardly of the direction of flight and is positioned to be substantially surrounded by the air stream adjacent the airborne vehicle for the creation of a suction effect on the outer end of the passage means to promote airflow therethrough.

3. A combination as set forth in claim 1 in which said remotely controlled means includes means on the airborne vehicle to detonate said explosive charge means in response to radio signals.

4. In combination with an airborne vehicle, means to provide visible signals for detection at great distances, comprising: a container for material capable of producing a visible signal in the atmosphere; a normally closed inlet air passage extending to said container'from the air stream adjacent said vehicle; a normally closed discharge passage extending from said container to the air stream adjacent the vehicle; a first. explosive charge to open said inlet passage in the upstreamdirection to receive ram air; a second explosive charge to open said discharge passage to permit'the ram air to forcesaid material out of the containerthrough.said' discharge passage -into the atmosphere; and remo-tecontrol ,nflt ans to the vehicle; and means to rotate said passage about an axis to create centrifugal force to urge said material through the passage.

7. A combination as settorth in claim 6 which includes means to direct a streamof ram air through said passage to cooperatewith the centrifugal force;

8. A combination as set forth in claim 6 which includes at least one explosive charge for detonation by said remote control means to opensaid passage.

9. A combination as set forth in claim 6 in-which said means to rotate said passage is aerodynamicmeans actuatcdby the air stream adjacent the airborne vehicle.

10. An aerial tow target comprising: a streamlined body for connection to. a tow cable; atleast onecontainer carried by said body enclosing material capable of creating a visible signal when 'dischargedinto the atmosphere; explosive means for opening up a path through the container. for discharge of said material from said container into the atmosphere; means to direct ram air along said path to promote the discharge of the material; and remote controls means including a signal-responsive means on, said tow target ,to detonate said explosive means.

ll. An aerial tow target comprising: a streamlined body for connection to a tow cable; at least one container onsaid body holding material capable of creating a visible signal when discharged into the atmosphere;passage means for discharging saidmaterial from the container into the atmosphere, said passage means extending outward laterallyof the axisof, said body; explosive means for opening up; a path forrelease of saidmaterial through said passage means; remote control means including a signal-responsiye means on said tow target to detonate said explosive means; and aerodynamic means responsive to the air stream adjacent saidlbody, to cause rotation of the .body aboutits longitudinal axis to rotate said discent the airborne vehicle for the creation of a suction effect on the discharge end thereof.

14. An aerial tow target comprising: a streamlined body for connection toa tow cable; a plurality of containers on sa id body enclosingmaterial capable of creating a visible signal when discharged into the atmosphere; a plurality of explosive meansincluding at least one for each container for opening up a path through the container for discharge of thematerial from the container;

means to direct rarn airalong said path to promote the discharge of saidrnaterial; a plurality of electrical means for detonating said explosive means; an electromotive source; and a remotely controlled stepping switchto connect said electromotivesource to. said detonating means in sequence.

15. A combination as set forth in claim 14 which includes a radio receiver in said body operatively connected to said stepping switch.

16. An aerial tow target comprising: a streamlined body for connection to a tow cable; a plurality of containers on said body enclosing material capable of creating a visible signal when discharged into the atmosphere; a corresponding plurality of normally closed. passage means for said containers respectively to dischargethe material therefrom into the atmosphere, each of said passage means extending laterally of the axis of said body; a corresponding plurality. of explosive means for said passage means respectively for opening up said passage means fordlscharge of material from the corresponding containers; a plurality of electrical means for .detonating said explosive means; an electromotive source; a remotely controlled stepping switch to connect said .electromotive source to said detonating means in sequence and aerodynamic means responsive to theair stream adjacent said body to cause rotation of said body along its longitudinal axis to rotate said plurality of passage means to create centrifugal force therein for; promotion of discharge fiow therethrough.

. References Citedin the file of this patent UNITED STATES PATENTS 2,47 6,302 Ieppson July 19, 1949 2,499,012 Welsh Feb. 28, 1950 2,899,606 Bates .Oct. 15, 1957 FOREIGN PATENTS 737,318 Great Britain Sept. 21, 1955 

